Transmission oil



mission gears.

Patented July 6, 1943 TRAN SDHSSION OIL Joseph S. Wallace, Whiting,Ind., assignor to Standard Oil Company, Chicago, 111., a corporation ofIndiana No Drawing. Application July 1, 1941, Serial No. 400,657

3 Claims.

The present invention relates to gear lubricants, and more particularlyto transmission oils.

In the past various kinds of oils and oil containing compositions havebeen used for trans- However, with the advent of automatic transmissiongears it has been necessary to improve the properties of the gearlubricants to a considerable extent. Whereas previously, the extremepressure properties of the oil were of the utmost importance it is nowessential to provide an oil having a high viscosity index and a low pourpoint as well. To obtain these addi tional qualities gear lubricants areat present prepared by admixing a heavy mineral oil having a viscosityindex approaching that desired in the gear lubricant, an extremepressure agent and a pour depressant to obtain the low pour point. Suchlubricating compositions-have a viscosity index of from about 70 toabout 100 and a pour point from l5 F. to F. Usually, however, it isdifficult to obtain a low pour point when using an oil of desiredviscosity having a high viscosity index. These lubricating compositionspresent various difficulties which seriously interfere with the properlubrication of gears. The heavy oils used are susceptible to oxidationand give products which have little or no lubricating value.

It is an object of the present invention to pro-' vide a lubricant whichavoids the above-mentioned difficulties. A further object is to preparea gear lubricant which is not easily oxidized and therefore retains itslubricating properties.

Still another object of the present invention is to provide a lubricantwhich meets rigid specifications as to pour point, flash point, firepoint, viscosity, extreme pressur properties, color and the like which,at the same time, is highly resistant to oxidation and carbon formationand has a high viscosity index.

According to th present invention the gear lubricant contains acomparatively light petroleum oil, an extreme pressure agent and a highmolecular weight hydrocarbon oil. The latter component, because of itshigh molecular weight, appearance and physical characteristics issometimes referred to as a resin or a resinous oil" even though itschemical characteristics are far different from those materials morecommonly and more properly known as resins. In order to distinguish thehigh molecular weight oil more clearly from the comparatively lightpetroleum oil in the following description, the former will be referredto hereinafter as a resin-like oil.

While light petroleum oils of differing characteristics may be used,depending on the nature and properties desired in the final product, ithas been found that from about to about of an oil having a viscosity offrom about 70. seconds Saybolt Universal at F. to about seconds SayboltUniversal at 100 F. and a viscosity index of less than 50 is suitable.Various types of extreme pressure agents, such as sulfurized sperm oil,sulfurlzed fatty oils, sulfurized fat, sulfurized isobutylene polymers,and other sulfur-containing extreme pressure agents may be usedinquantities ranging from about 1% to about 15% of the total composition.

The resin-like oil has a molecular weight of from about 1000 to about2000 and may be added in quantities ranging from about 10% to about 30%but preferably from about 17% to about 20% of the composition. Thisresin-like oil may be obtained preferably from a Pennsylvania cyl-'inder stock which has been dewaxed at about -40 F. The dewaxed stock isthen treated with four to ten volumes of propane at a temperature fromabout F. to about F. to produce two phases, a lighter propane-solublephase and aheavy propane-insoluble phase containing the resin-like oils.The heavy fraction is then treated with additional propane at from 135F. to 155 F., usually about 145 F., the ratio of propane to heavy oilbeing from about 5 to l to about 10 to l, and usually about '7 to 1. Bythis treatment about 3% to about fil /2% of the resin-like oil based onthe original amount of dewaxed oil precipitates out from thepropane-soluble constituents of the heavy oil. Although propane has beenreferred to as the refining agent it will be understood that the propanemay contain or be replaced by other normally gaseous hydrocarbons,particularly ethane, isobutane, butane, propylene, butylene, etc. Thisresin-like oil is a substantiall wax-free and asphalt-free producthaving a Saybolt Universal viscosity at 210 F. of from about 1000 toabout 4000 or more seconds, a viscosity index of about 90 or more and arelatively high pour point. The characteristics of a specific exampleare as follows: I

Gravity=A. P. I. 16.7 Flash point=615 F. Fire point=720 F.

Viscosity at 210 Ff=2910 seconds Saybolt Universal Viscosity index=95Pour point (natural) =60 F.

mixed base oil such as Mid-Continent. Obviously in this case it would benecessary to deasphalt as well as dewax theoil before precipitation ofthe resin-like oil. When a Mid-Continent oil is used the asphalt mayberemoved by treatment with propane at temperatures of from 105 F. to 115F.. the oil-propane ratio being about 1 to 2.

A more detailed description of the process for obtaining the'resin-likeoil will be found in U. 8. Patents 2,143,872 and 2,143,882.

An example of a transmission oil according to the present inventioncontains:

Oil (viscosity of 85 seconds at 100 F., V. 1.

less than 50 and 300 F. min. flash) '73 Resin-like 17 Sulfurized spermoil A lubricant having the foregoing composition has the followingproperties and characteristics:

Almen failure (extreme pressure) Passes maximum 30 lb. load Copper strip(3 hrs. at 200 F.) No corrosion Heating test (125 hrs. at 200 F.)

Evaporation loss per cent 0.9 Residue ppt, None vis. incr. at 210 F 31%decrease Vis. incr. at 130 F .5% decrease It will be noted that thislubricant has an exceedingly high viscosity index, excellent extremepressure properties and low pour point. In Table I below, thecharacteristics of three transmission oils without'the resin-like oilare compared with a lubricant according to the present invention.

Per cent:

Saponifiable oil -per cent 7.6 Added sulfur do 1.1 Total sulfur M 2.2Flash point F 320 Fire poi 9 IL- 370 Pour point (shock chilling) 1 25 S.U. vis. at 210 F 58 8. U. vis. at 130 F 176 S. U. vis. at 100 F 365Viscosity index 108 Ash --per cent 0.015 Moisture do Trace Thecharacteristicso'f base oils Nos. 1 to 4 inclusive are given in thefollowing Table II:

Tana: II-

' Characteristics of base oils on Viscosi Visoosit Viscosity Pour at 100at 210 index point F. 31: 48 Below to o 314 so on +15 ass as. a 92.4 0as as. 0 Below to 25 The pour depressant referred to in the above TableI is of the type obtained by the condensation of a halogenated longchain aliphatic hydrocarbon such as chlorinated parafiln wax, with anaromatic hydrocarbon such as naphthalene in the presence of aFriedel-Crafts catalyst such as aluminum chloride. It is' clearlyevident from Table I that whenever an eifort was made to improve theviscosity index of the lubricant, the pour point rose above the minimumrequirement. However,

the lubricant containing the resin-like oil and without a pourdepressant not only gives an excellent viscosity index but also meetsthe maximum pour point requirements.

With reference to the present invention attention is called totheapplication of Claron N. White and Frederick H. MacLaren filed June 30,1941, Serial No. 400,460, entitled Lubricants.

Although the present invention has been described with reference tospecific examples, these are not to be construed as limitations. Thescope of the present invention is defined by the appended claims.

V I claim: Y 1. An extreme pressure lubricant suitable for use as atransmission lubricant containing from about 55% to about of a minerallubricating oil having a relatively low viscosity index anda viscosityof from about 70 to about 150 seconds Saybolt Universal at F., fromabout 1% to about 15% of a sulfur-containing extreme pressure agent andfrom about 10% to about 30% of a resin-like oil obtained by treating asubstantially asphalt-free, wax-free lubricating oil stock with aliquefied normally gaseous hydrocarbon to effect a phase separation of alight fraction soluble in said liquefied hydrocarbon and a heavyfraction containing the resin-like oil insoluble in said liquefiedhydrocarbon, and precipitating the resin-like oil from said heavyfraction by treating said heavy fractionwith further amounts of theliquefied normally gaseous hydrocarbon.

2. An extreme pressure lubricant suitable for use as a transmissionlubricant as claimed in claim 1 wherein the percentage range ofresinlike oil is from about 17% to about 20%.

3. An extreme pressure lubricant suitable for use as a transmissionlubricant as claimed in claim 1 consisting of 73% of the minerallubricating oil, 10% of sulfurized' sperm oil and 17% of the resin-likeoil.

JOSEPH B. WALLACE.

